The present invention relates to a method and apparatus for incorporating an identifying resistance into a fuel injector to provide an indication of characteristics of the particular injector .
Fuel injectors are utilized to assist in the injection of fuel during operation of a diesel engine. With manufacturing tolerances, etc., each fuel injector has distinct characteristics. Fuel injectors have two characteristics that a re important to control of the fuel injection process. First, an offset characteristic is defied, and second, a slope of change of the fuel injection ability is defined. As these two characteristics vary, an optimum control for the particular fuel injector also varies. Thus, an optimum control would be aware of the characteristics for a particular injector.
An OEM customer of applicant""s has proposed that each fuel injector be tested to determine both the offset and slope, an d that an identifier be put into the fuel injector to tell an engine control the offset and slope which applies for the particular injector. The OEM proposed having a dedicated control, such as a microprocessor, incorporated into the fuel injector to send an identifying signal.
The present invention is directed to achieving the identification with a much simpler and lower cost solution.
In a disclosed embodiment of this invention, a fuel injector is tested after assembly, and its offset and slope determined. The offset and slope information is then used to characterize the fuel injection into one of several particular types. A characterization resistor of a value indicative of the xe2x80x9ctypexe2x80x9d of injector is then incorporated into a circuit associated with the fuel injector. The diesel engine control can query the fuel injector, and read the voltage due to the characterization resistor to determine the xe2x80x9ctypexe2x80x9d of fuel injector. The xe2x80x9ctypexe2x80x9d is then associated with a particular offset and slope for the fuel injector. The control will then know how to optimally control the particular fuel injector.
In a preferred embodiment of this invention, the fuel injector is provided a coil to open the injector, and a separate coil to close the injector. Each coil is provided with a high side and a low side driver which are powered to operate the coils in normal operation.
As the engine is being started, the system automatically scans the characterization resistor of each injector to determine each cylinder""s injector xe2x80x9ctypexe2x80x9d. Identification current is passed through the characterization resistor, which is connected to the high side of coil A and the low side of coil B. By applying the xe2x80x9c48 Vxe2x80x9d power to a resistor network and returning the current to ground via the low side driver. T he voltage across the characterization resistor is measured at the high side of coil A . This voltage is then associated with a prestored code, which in turn tells the control which type of fuel injector is associated with the particular voltage. The present invention thus provides a simple way of identifying each fuel injector type. One particular benefit of this invention is that the wire harness to the fuel injector need not have any additional wire to provide the identification feature.
A control method is also disclosed wherein the identification of the particular fuel injector is only performed if the temperature of the control module is below a predetermined temperature. Applicant recognizes that if the control module is above a relatively high predetermined temperature, then the vehicle has not been stopped for any length of time. The need to redetermine each fuel injector type only occurs when a fuel injector has been replaced. The replacement of a fuel injector would require a long shutdown time for the engine. If the temperature of the control is above the predetermined temperature, an assumption can be made that the vehicle has not been shut down long enough to replace a fuel injector.
However, if the control temperature is below the predetermined temperature, then it is possible a fuel injector has been replaced. Of course, it may also simply be the vehicle has been shut down for a length of time, but no fuel injectors have been replaced. Even so, in a preferred method, in such a situation, each of the fuel injectors are again queried. A control signal is sent to each of the fuel injectors, and the voltage from the characterization resistor is read. The voltage is again associated with a particular type of fuel injector, and the particular type of fuel injector is stored at the control. The control then knows how to optimally operate the particular fuel injector.
A second distinct feature of this invention relates to the types of characteristics associated with an identifying quantity which increases. The increasing quantities increase such that each next voltage is assigned to a combination of the two characteristics that only changes in one of the two characteristics. This will be explained with reference to a two-dimensional array, where the xe2x80x9ctypesxe2x80x9d are stored in a spiral fashion.